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前言：
在销售医药产品时，如果是中药销售，因为没有批号，所以将查询出来的数据全部按单位进行合并其库存后再销售
一、创建Product类
@Data
public class Product {
/**id*/
private String productId;
/**库存*/
private double stockCount;
/**采购数量*/
private double purchaseCount;
/**单位*/
private String unit;
}
方法一：通过java的map来实现
List list = new ArrayList();
list.add(new Product(1, 10, 10));
list.add(new Product(2, 11, 11));
list.add(new Product(1, 12, 12));
//如果是中药，合并库存
Map map = new HashMap();
for (Product productVO : list) {
String id = productVO.getProductId();
if (map.containsKey(id)) {
Product s = map.get(id);
String unit = s.getUnit();
if (“KG".equalsIgnoreCase(unit) ||"千克".equalsIgnoreCase(unit) || "克".equalsIgnoreCase(unit) || "g".equalsIgnoreCase(unit)) {
s.setStockCount(s.getStockCount().add(productVO.getStockCount()));
s.setPurchaseCount(s.getPurchaseCount().add(productVO.getPurchaseCount()));
}
map.put(id, s);
} else {
map.put(id, productVO);
}
}
List newList = new ArrayList();
for (String temp : map.keySet()) {
newList.add(map.get(temp));
}
System.out.println(newList );
方法二：通过Lamba表达式的groupingBy来实现
List list = new ArrayList();
list.add(new Product(1, 10, 10));
list.add(new Product(2, 11, 11));
list.add(new Product(1, 12, 12));
List newList = new ArrayList();
list.parallelStream().collect(Collectors.groupingBy(Product::getProductId, Collectors.toList()))
.forEach((id, stu) -> {
stu.stream().reduce((a, b) -> new Product (a.getProductId(), a.getStockCount() + b.getStockCount(), a.getpurchaseCount() + b.getpurchaseCount())).ifPresent(newList ::add);
});
System.out.println(newList );
方法三：使用Lamba表达式的toMap来实现
List removalList = saleOrderDetails.stream()
.collect(Collectors.toMap(Product::getProductId, a -> a, (o1, o2) -> {
o1.setStockCount(o1.getStockCount().add(o2.getStockCount()));
o1.setSaleCount(o1.getSaleCount().add(o2.getSaleCount()));
o1.setSellAmount(o1.getSellAmount().add(o2.getSellAmount()));
return o1;
}))
.values()
.stream()
.filter(d -> {
return Objects.equals(d.getIsRxDrug(), 1) && Objects.equals(d.getIsNeedPrescription(), 1);
})
.collect(Collectors.toList());
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